1. Field of the Invention
The present invention is related to a compression coding of a video signal, and more particularly, to a device and method for coding an audio/video signal, in which a sampling rate is shifted according to a variance of a received data during data sampling operation for improving a coding efficiency.
2. Background of the Related Art
A related art audio/video coding will be explained with reference to the attached drawings. FIG. 1a illustrates a block diagram of a related art encoder for coding an audio/video signal, and FIG. 1b illustrates a block diagram of a related art decoder for decoding an audio/video signal.
The related art encoder, mostly provided in a transmitter block in a video data transmission/reception device is provided with a low pass filter 1 for low pass filtering an analog video signal X(t) to remove a noise from a high frequency region thereof, a sample/hold unit 2 for sampling the video signal filtered by the low pass filter 1 at a fixed sampling rate, a quantizing unit 3 for quantizing a sampled/held signal, and an encoding block 4 for compressing a data from the quantizing unit 3 to provide an encoded digital signal. And, the related art decoder is provided with a decoding block 5 for decoding the encoded digital signal, an inverse quantizing unit 6 for inverse quantizing the decoded video signal, a DAC 7 for converting the inverse quantized video data into analog signal, and a low pass filter 8 for low pass filtering the video data converted into the analog signal.
A data coding operation in the aforementioned related art device for coding an audio/video will be explained. FIG. 2 illustrates sampling spectrums in a related art coding operation, and FIG. 3 illustrates a related art coding operation sequence of an audio/video signal. A related art sequence of video data compression/encoding is as follows.
First, upon reception of an analog video signal X(t), the analog video signal X(t) is filtered at the low pass filter 1, to remove a noise in a high frequency region thereof. Then, the filtered video signal is sampled at a fixed sampling rate at the sample/hold unit 2. The sampled/hold signal is quantized at the quantizing unit 3, and the quantized data is compressed/encoded at the encoding block 4, to provide a digital video signal.
Because the data sampling rate is fixed in the related art audio/video signal coding regardless of a variance of the received data, a sampling error is liable to occur if the variance of the received data is great and a volume of sampling data becomes too great unnecessarily if the variance of the received data is small. That is, in the related art coding of an audio/video signal, a sampling error eA or eB as shown in FIG. 2 is generated if the variance of the received data is great because the sampling rate is fixed in data sampling operation. And, a volume of the sampled data becomes too great unnecessarily even though a smaller volume of data is satisfactory if the variance of the received data is smaller because the data sampling operation is made according to the fixed sampling rate.
Accordingly, the present invention is directed to device and method for coding an audio/video signal that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide device and method for coding an audio/video signal, in which a sampling rate is shifted according to a variance of a received data in a data sampling operation, for improving a coding efficiency.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device for coding an audio/video signal includes a first sample/hold unit for sampling/holding an analog video signal at a first sampling rate in response to a sampling control signal, a phase shifter for shifting a phase of the sampling control signal according to a variance of the video signal, a second sampling/hold unit for sampling/holding an analog video signal at a second sampling rate in response to the sampling control signal shifted by the phase shifter, a summer for summing the sampling data from the first sample/hold unit and the sampling data from the second sample/hold unit, a comparator for comparing the sampling data summed at the summer to an arbitrarily set critical value, a switching unit for selectively providing the sampling data either from the first sample/hold unit or from the second sample/hold unit in response to a signal from the comparator, a quantizing unit for quantizing the sampling data selectively provided by the switching unit, and an encoding block for compressing a data from the quantizing unit, to provide an encoded data.
In other aspect of the present invention, there is provided a method for coding an audio/video signal, including the steps of (1) sampling a filtered video signal at a fixed sampling rate and a shifted sampling rate, (2) summing a sampled data of the fixed sampling rate and a sampled data of a shifted sampling rate, and comparing to an arbitrary critical value, and (3) as a result of the comparison of the summed sampled data to the arbitrary critical value, the sampled data of the fixed sampling rate is forwarded if a summed output is not smaller than the critical value, and the sampled data of the shifted sampling rate is forwarded if the summed output is smaller than the critical value.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.